Operator cab for construction machine

ABSTRACT

An operator cab  53 , which is mounted rotatable on the vehicle body  51  of a hydraulic mini-shovel  50 , comprises a cab box  1 , a door  2 , upper and lower link members  3  and  4 , a slide member  6 , a closed door lock  7 , an opened door lock  9  and a handle  13 . The cab box  1  has an internal cab room  1   a  and an entrance  15 , which leads into the cab room  1   a . The door  2  closes and opens the entrance  15  when it is moved forward and rearward, respectively. The upper and lower link members  3  and  4  have fixed ends  3   a  and  4   a , each of which is connected pivotally to the cab box  1 , and moving ends  3   b  and  4   b , each of which is connected pivotally to the front end of the door  2 . The slide member  6  is connected pivotally to the rear end of the door  2  so as to swing freely and slides along a slide rail  5 , which is provided externally on the cab box  1 . The closed door lock  7 , which is provided at the front end of the door  2 , engages with a closed door striker  8 , which is provided on the cab box  1 , when the door  2  is closed. The opened door lock  9 , which is provided at the front end of the door  2 , engages with an opened door striker  10 , which is provided on the cab box  1 , when the door  2  is opened. The handle  13  is provided at the front end of the door  2  and interlocked with the closed door lock  7  and the opened door lock  9.

FIELD OF THE INVENTION

The present invention relates generally to an operator cab used for aconstruction machine and particularly to an operator cab for aconstruction machine which has an entrance door.

BACKGROUND OF THE INVENTION

Construction equipment such as a hydraulic mini-shovel comprises anoperator cab and a construction machine, which are provided on a vehiclebody, so that they are easily turned around for performing constructionwork. While work is being performed, the door of the operator cab,through which an operator gets into or out of the cab, is usuallyclosed, but it is sometimes kept open. FIG. 10 shows a largeconstruction machine 60. It comprises a turret 62, which is providedrotatable on a vehicle body 61, and an operator cab 63, which is mountedon the turret 62. In a case like this large construction machine 60, theturning radius R′ of the turret 62 is relatively large, so the door 64of the cab 63 never exceeds the turning radius R′ even in its openedcondition. However, in a case of a small construction machine, as theturning radius is accordingly small, there is a probability that thedoor in its opened condition exceed the turning radius. To solve thisproblem, there is known an operator cab for a construction machine, thedoor of which cab is designed not to exceed the turning radius even inits opened condition (for example, refer to Japanese Laid-Open PatentPublication No. H04(1992)-353129). In this operator cab, the door slidesback and forth along a rail and along the outer periphery of the cab ina top view, and the side of the cab that includes the door is curvedconvex in a top view, so that the door in its opened condition neverexceeds the turning radius of the cab.

PROBLEMS TO BE SOLVED BY THE INVENTION

In a case where the door slides back and forth along a rail, a handleused to open or close the door is provided on a side toward which thedoor closes (this side is referred to as “front side”) while a lock tomaintain the opened and closed conditions of the door is provided on aside toward which the door opens (this side is referred to as “rearside”). To support this design, at the central part of the door, amechanism is provided to connect the handle and the lock and to engageor disengage the lock to or from a striker. Because of such acomplicated design of the door, there are following problems. The dooris thick and heavy, so the manufacturing cost of the door is relativelyhigh. Also, because of the mechanism placed at the central part of thedoor, a window is not available for outside view on the door.Furthermore, as for operability in opening and shutting the door,rollers and a slide rail constituting a slide mechanism present roughmovements for the opening and closing of the door. The door just beforeits complete closure rubs the cab on the front side and moves along thelateral face of the cab on the rear side. This makes not only the feelof the door operation awkward but also makes the seal of the doormalfunction, causing leakage.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an operator cab fora construction machine which cab has a door to be opened and closedthrough a link mechanism that connects pivotally the front side of thedoor to a cab box and through a slide mechanism that connects the rearside of the door to the cab box.

An operator cab according to the present invention is provided for aconstruction machine, and the operator cab comprises a cab box, a door,a link member, a closed door lock, an opened door lock and a handle. Thecab box has an internal cab room and an entrance into the cab room, andthe door is attached at the entrance such that the entrance is closedwhen the door is moved forward, and it is opened when the door is movedrearward. One end of the link member is connected pivotally to the cabbox while the other end is connected pivotally to the front end of thedoor, the link member being capable of freely swinging horizontally. Theclosed door lock is provided at the front end of the door to engage witha closed door striker, which is provided on the cab box. The closed doorlock is to keep the front end of the door at a closed position, wherethe entrance is closed, after the door has shifted forward incorrespondence to a forward swing of the link member around a pivot atthe one end thereof and has reached the closed position. The opened doorlock is provided also at the front end of the door to engage with anopened door striker, which is provided on the cab box. The opened doorlock is to keep the door open after the door has shifted rearward incorrespondence to a rearward swing of the link member around the pivotof the one end thereof and has opened. The handle is provided also atthe front end of the door and interlocked with the closed door lock andwith the opened door lock to release the closed door striker or theopened door striker from engagement.

As a construction machine to which the present invention relates, thereis such a construction machine as a hydraulic mini-shovel 50, whosevehicle body supports an operator cab rotatably as mentioned in thefollowing embodiment.

It is preferable that the link member comprise an upper link member anda lower link member, which are connected pivotally to the upper frontend and the lower front end of the door, respectively, the upper andlower link members being capable of freely swinging horizontally. It isalso preferable that the lower link member be provided below the floorof the cab box, so that the lower link member never intrudes the cabroom.

Furthermore, at the rear end of the door, a rear slide member may beprovided to slide back and forth along a slide rail, which is providedexternally on the cab box, the slide rail extending in theback-and-forth direction, so that the rear end of the door can slideback and forth with respect to the cab box by the rear slide member. Inthis case, preferably, the slide rail is provided approximately at thevertical center of the external surface of the cab box in rear of theentrance, the slide rail extending in the back-and-forth direction.

On the other hand, the rear end of the door may be attached to the rearside of the entrance of the cab box by a rear link member, whose one endis connected pivotally to the cab box and whose other end is connectedpivotally to the rear end of the door, the rear link member capable offreely swinging horizontally.

Furthermore, it is preferable that part of the side of the cab boxincluding the door in its closed condition be flat and extend linearlyin the back-and-forth direction in a top view.

By constructing the operator cab for a construction machine in a way asdescribed above according to the present invention, a good feel of thedoor operation, i.e., the opening and closing of the door, is achievedbecause the movement of the door just before the complete closure isdirected inward in a similar way as a prior-art hinged door. This inwardmovement of the door at the final moment of the closing pushes a sealmember, which is provided to seal the door to the cab box, head-on, sothe seal member achieves a high endurance and a high watertightness.Furthermore, the present invention provides an improved safety becausethe door never drops off from the cab box even if the slide member comesout of the slide rail accidentally, because the front part of the dooris supported by the link members. Moreover, because the handle and thelocks, which fix the door in its opened condition or in its closedcondition, are provided in concentration at the front end of the door,the construction of the door is relatively simple. Therefore, thepresent invention achieves reductions in the weight of the door as wellas in the manufacturing cost and enables the door to have a window atthe central part of the door, the window widening the field of view fromthe inside of the operator cab.

Additionally, the link members, which comprise upper and lower linkmembers at the upper and lower ends, respectively, of the door,contribute to the improvement in the feel of the door operation becausethis arrangement of the link members eliminates any looseness in thesupport of the front part of the door. Furthermore, as the lower linkmember is arranged never to enter the cab room, the safety andconvenience of the operator getting into and out of the operator cab arenot jeopardized. Moreover, the positioning of the slide railapproximately at the vertical center facilitates the smoothness of thedoor operation.

According to the present invention, the part of the side of the cab boxthat includes the door extends linearly in a top view. This designenables to provide relatively large widths for the front and the rear ofthe operator cab and thereby secures a wider space especially at thefeet of the operator in the cab room.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawingswhich are given by way of illustration only and thus are not limitativeof the present invention.

FIG. 1 is a side view of an operator cab for a construction machine as afirst embodiment according to the present invention.

FIG. 2 is a side view of a construction machine as an example whichincorporates an operator cab according to the present invention.

FIG. 3 is a plan view of important parts of the operator cab as thefirst embodiment, with its door closed.

FIG. 4 is a plan view of the same important parts of the operator cab asthe first embodiment, with its door opened.

FIGS. 5A and 5B are views showing important parts of a slide mechanismof the first embodiment, including an opened door stopper. FIG. 5A is atop view while FIG. 5B is a rear view.

FIG. 6 is a plan view of important parts of the slide mechanism of thefirst embodiment, including a closed door stopper.

FIG. 7 is a plan view showing the path the door of the first embodimenttrack through when it is opened and it is closed.

FIGS. 8A and 8B are plan views showing the contour of the operator cab.FIG. 8A shows the cab with its door closed while FIG. 8B shows the cabwith its door opened.

FIGS. 9A and 9B are views of a link member with a roller, which isprovided in the first embodiment. FIG. 9A is a top view while FIG. 9B isa side view.

FIG. 10 is a plan view of a prior-art, large construction machine.

FIG. 11 is a side view of an operator cab for a construction machine asa second embodiment according to the present invention.

FIG. 12 is a plan view of important parts of the operator cab as thesecond embodiment, with its door closed.

FIG. 13 is a plan view of the same important parts of the operator cabas the second embodiment, with its door opened.

FIG. 14 is a side view of an operator cab for a construction machine asa third embodiment according to the present invention.

FIG. 15 is a plan view of important parts of the operator cab as thethird embodiment, with its door closed.

FIG. 16 is a plan view of the same important parts of the operator cabas the third embodiment, with its door opened.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments according to the present invention aredescribed in reference to the drawings. Before an operator cab accordingto the present invention is described, a hydraulic mini-shovel 50 as anexample of construction machine that incorporates an operator cab isdescribed in reference to FIG. 2. The mini-shovel 50 comprises a vehiclebody 51 and a swivel base 52. The vehicle body 51 includes a crawlerdevice by which it is capable of traveling. The vehicle body 51 supportsrotatably the swivel base 52, so that the swivel base 52 can rotatehorizontally with respect to the vehicle body 51, and an operator cab 53and an engine room 54 are provided on the swivel base 52. In addition, awork device 55 is provided pivotally in front of the cab on the swivelbase 52, and the work device 55 is driven by hydraulic cylinders, sothat it can stretch and bend to perform a desired work. On a side of thecab box 1, which constitutes the operator cab 53, there is a door 2,which is opened and closed for an operator to get into or get out of theoperator cab 53.

First Embodiment

Now, the construction of a door 2 as a first embodiment, which isattached to the operator cab 53, is described in reference to FIG.1˜FIG. 8. In the following description, the direction of the closing ofthe door is referred to as “forward” (arrow F in FIG. 1). As shown inFIG. 1, the door 2, whose front side is attached to the cab box 1 by alink mechanism 20 and whose rear side is attached to the cab box 1 by aslide mechanism 30, opens and closes an entrance 15 to the cab room 1 a,which is defined by the cab box 1. The link mechanism 20 comprises anupper link member 3, which is located at the upper part of the door 2,and a lower link member 4, which is located at the lower part of thedoor 2. One end of each link member is connected pivotally to the cabbox 1, and the other end is connected pivotally to the door 2, so thatthe link members can swing freely. On the other hand, the slidemechanism 30, which is positioned approximately at the vertical centerof the entrance 15, comprises a slide rail 5, which is provide on theexternal side of the cab box 1, and a slide member 6, which slides alongthe slide rail 5.

As mentioned above, the upper and lower link members 3 and 4, whichconstitute the link mechanism 20, one ends (fixed ends 3 a and 4 a) areconnected pivotally to the cab box 1 so as to swing freely while theother ends (3 b and 4 b) are connected pivotally to the upper and lowerfront ends of the door 2 so as to swing freely as shown in FIG. 3 andFIG. 4. In these plan views, the pivots of the fixed ends 3 a and 4 a ofthe upper and lower link members 3 and 4 are oriented vertically oneabove the other, so the upper and lower link members 3 and 4 rotate orswing around the fixed ends 3 a and 4 a when the door 2 opens and closesas shown in FIG. 3 and FIG. 4. The fixed end 4 a of the lower linkmember 4 is positioned lower than the floor of the cab box 1, so thelower link member 4 including the fixed end 4 a never enter the cab box1 (cab room 1 a). This design facilitates the safety as well as the easeof the getting on and off of the operator.

As mentioned above, the slide mechanism 30 comprises a slide rail 5,which extends in the back-and-forth direction behind the entrance 15 andapproximately at the vertical center of the entrance 15 outside the cabbox 1, and a slide member 6, which is attached to the door 2 and slidesalong the slide rail 5, as shown in FIG. 1, FIG. 5 and FIG. 6. The sliderail 5 has a groove whose open side faces outward, and the outward endof the upper side of the groove is bent downward to form a rail groove 5a. The slide member 6, which is attached on the rear inside (the sidefacing the cab box 1) part of the door 2 approximately at the verticalcenter thereof comprises a bumper 6 a, which fits with stoppers 11 and12 described later, a rocker 6 b, which is connected pivotally to thebumper 6 a so as to swing freely, and guide rollers 6 c and a centerroller 6 d, which are positioned in the groove of the slide rail 5 so asto slide inside the groove.

In a condition where the slide member 6 is attached to slide along theslide rail 5, the guide rollers 6 c, which are positioned in the railgroove 5 a of the slide rail 5, roll and slide along the rail groove 5a, and the center roller 6 d rolls and slides along the lower side 5 bof the groove of the slide rail 5. Because the outward end of the upperside of the slide rail 5 is bent downward, defining the rail groove 5 a,as mentioned above, the guide rollers 6 c never go out of the railgroove 5 a, so they securely guide the sliding of the slide member 6along the rail groove 5 a. Also, because the rocker 6 b of the slidemember 6 can swing with respect to the bumper 6 a, the door 2 swivelingthe rocker 6 b can slide even though the slide rail 5 is bent as shownin FIG. 6.

At the front part of the door 2, a closed door lock 7 is provided tokeep the closed condition of the door 2, and the closed door lock 7 isengaged with a closed door striker 8, which is provided at the part ofthe cab box 1 facing the closed door 2 (at the front of the entrance 15)as shown in FIG. 3. Also, at the front part of the door 2, an openeddoor lock 9 is provided to keep the opened condition of the door 2, andthe opened door lock 9 is engaged with an opened door striker 10, whichis provided at the part of the cab box 1 facing the opened door 2 (atthe rear of the entrance 15) as shown in FIG. 4. In this embodiment, theclosed door lock 7 and the opened door lock 9, which are provided at thefront part of the door 2, are embodied as separate parts. However, theycan be designed as a common part in another embodiment.

The cab box 1 is provided with an opened door stopper 11, which fitswith the bumper 6 a at the rear part of the door 2 when the door isopened, keeping the opened condition of the door, and with a closed doorstopper 12, which fits with the bumper 6 a at the rear part of the door2 when the door is closed, keeping the closed condition of the door. Theopened door stopper 11 comprises a bracket 11 b, which is mounted inrear of the slide rail 5, and a protruding part 11 a, which is mountedon the bracket 11 b and extends (in the back-and-forth direction)approximately in parallel with the slide rail 5 as shown in FIG. 5. Theclosed door stopper 12 comprises a bracket 12 b, which is mounted infront of the slide rail 5, and a protruding part 12 a, which is mountedon the bracket 12 b and extends outward with respect to the cab box 1 asshown in FIG. 6. The opened door stopper 11 and the closed door stopper12 are designed such that the protruding part 11 a or the protrudingpart 12 a fits with the bumper 6 a of the slide member 6 when the dooris opened or closed, respectively. The protruding part 11 a of theopened door stopper 11 fits with the bumper 6 a when it enters a fittingrecess 6 e provided on a side of the bumper 6 a as shown in FIG. 5. Onthe other hand, the protruding part 12 a of the closed door stopper 12fits with the bumper 6 a when it enters a fitting recess 6 f provided atthe end of the bumper 6 a as shown in FIG. 6. In addition, the openeddoor stopper 11 functions to prevent the slide member 6 from going outof the respective end of the slide rail 5.

In a case of a prior-art door whose front and rear slide, a tab tail (apart of a mechanism in which a convex is inserted into a concave forfixation) is provided at the front part of the door for fixing theopened door, and a mating part is provided on (a center pillar part of)the cab box. In this case, because clumsy brackets for mounting the tabtail are required at the front upper and lower ends of the door, thebrackets obstruct the view and impair the safety. Moreover, becausestoppers are mounted on the rear external side of the cab box,protruding outward, this design is not good in appearance and safety. Onthe other hand, in the embodiment according to the present invention,only the opened door stopper 11, which is for fixing the rear part ofthe door, is provided externally along the rear part of the slide rail5. The closed door stopper 12, the bumper 6 a and the like are providedinside the door 2, so they are not visible from the outside. As aresult, the operator cab according to the present invention providesimprovements in appearance (external design) and safety and in the rangeof vision.

At the front part of the door 2, a handle 13 is provided for opening andclosing the door 2 from the inside and outside of the cab box 1. Thehandle 13 is used to release the engagement between the closed door lock7 and the closed door striker 8 for opening the door 2 or to release theengagement between the opened door lock 9 and the opened door striker 10for closing the door 2. Because the mechanism used for opening andclosing the door 2 is provided integrally at the front part of the door2 (approximately at the vertical center in FIG. 1), the construction ofthe door 2 is relatively simple. As a result, the door 2 can be madethinner, and the door, which has been press-molded conventionally, canbe now made with a pipe frame. In this way, it is possible to reduce theweight as well as the manufacturing cost of the door 2. Furthermore, thedoor 2 can be provided with a window 14 at the central part of the door2 to increase the field of vision from the inside of the cab box 1.

As shown in FIG. 3, which shows the door 2 in its closed condition, whenthe door 2 is closed, the closed door lock 7, which is provided at thefront part of the door 2, engages with the closed door striker 8, fixingthe front part of the door. At the same time, the protruding part 12 aof the closed door stopper 12 fits with the fitting recess 6 f of thebumper 6 a of the slide member 6, fixing the rear part of the door. Inthis condition, the front part of the door 2 is fixed on the cab box 1without any looseness as it is supported by the upper and lower linkmembers 3 and 4.

As shown in FIG. 4, which shows the door 2 in its opened condition, whenthe door 2 is opened, the opened door lock 9, which is provided at thefront part of the door 2, engages with the opened door striker 10,fixing the front part of the door. At the same time, the protruding part11 a of the opened door stopper 11 fits with the fitting recess 6 e ofthe bumper 6 a of the slide member 6, fixing the rear part of the door.In this condition, the front part of the door 2 is fixed on the cab box1 also without any looseness as it is supported by the upper and lowerlink members 3 and 4.

In this embodiment, as the door 2 is supported by the link mechanism 20,the door 2, which is retained by the link mechanism 20, will not comeoff from the cab box 1 even if the slide member 6 comes out of the sliderail 5. In this way, the present invention provides an improved safety.

There is a clearance between the slide rail 5 and the guide rollers 6 cand center roller 6 d of slide member 6 for these rollers to rotate, andthe rocker 6 b, which retains the guide rollers 6 c and the centerroller 6 d, swings with respect to the bumper 6 a. The clearance and theswing cause the rear part of the door 2 to be a little shaky during theopening and closing. However, the door 2 is secured without loosenesswhen the opened door stopper 11 and the closed door stopper 12 engagewith the bumper 6 a of the slide member 6 to fix the door 2,respectively when the door 2 is opened and when it is closed asmentioned above. Furthermore, because the fitting recesses 6 e and 6 fthat fit with the stoppers 11 and 12 for fixing the door 2 are providednot as separate parts but as part of the bumper 6 a of the slide member6, the side of the cab box 1 is smooth without protrusions that mayimpair the external look of the operator cab.

Now, the movement of the door 2, which is constructed as describedabove, is described in reference to FIG. 7. As mentioned above, thefront part of the door 2 is swung by the link mechanism 20 while therear part is slid by the slide mechanism 30. As a result, the path ofthe door 2 during the opening and the closing is determined by the linkmechanism 20 and the slide mechanism 30, so the front end of the doormoves along track C1 indicated in FIG. 7 while the rear end moves alongtrack C2. As far as the track of the door just before the completion ofthe closing is concerned, the front end moves inward in the directionindicated by arrow A in FIG. 7, and this movement is similar to that ofa hinged door. In a case of a prior-art door whose front and rear slide,the track of the door just before the complete closure is toward adirection (inward) different from the rotational direction(back-and-forth direction) of the rollers, which rotate along the rail.Therefore, just before the door completely closes, the rollers stoprotating and slide, making the door feel heavier for the operator. Thisresults in a bad feel of the door operation. On the other hand, in thecase of the embodiment according to the present invention, the door doesnot become heavier at the final moment of the closing as the linkmechanism 20 swings, so the present invention provides a good feel ofthe operation. Furthermore, in a case of a door whose front slide, thereis looseness, which makes a bad feel of the door operation, but in thecase of the present invention, there is no looseness as the front partof the door 2 is supported by the link mechanism 20. As a result, thepresent invention provides a good feel of the door operation. Moreover,a seal member (not shown), which is provided on the door 2 to seal thedoor to the cab box 1, is pushed in the direction indicated by arrow Ain FIG. 7 when the door is closed, so the seal member never slides as inthe case of the prior-art sliding door. As a result, the operator cabaccording to the present invention can have a high endurance andwatertightness.

As shown in FIG. 3, the direction of the closed door stopper 12 to thefitting recess 6 f is set in parallel with the sliding direction E ofthe slide member 6, which has an angle θ with respect to the direction Dperpendicular to the line connecting the fixed ends 3 a and 4 a of theupper and lower link members 3 and 4 or the engaging point of the closeddoor lock 7 with the closed door striker 8 and the pivot of the slidemember 6. Therefore, the rear part of the door 2 moves in the directionindicated by arrow B in FIG. 7 in correspondence to the shape of theslide rail 5 other than in the direction indicated by arrow A when thedoor closes completely. Then, the closed door lock 7 engages with theclosed door striker 8 at the front part of the door 2 to fix the door.In this closed condition, the door 2 is fixed without looseness.Furthermore, the slide mechanism 30 enables the rear part of the door 2to slide into the side of the cab box 1, so that the rear part of thedoor 2 is positioned approximately in the same plane as the cab box 1when the door 2 is closed. In this closed condition, the rear part ofthe door 2 does not protrude from the side of the cab box 1.

As for the shape of the operator cab 53 (cab box 1), the part 1 a of theside of the cab box 1 where the door 2 is attached on the cab box 1extends linearly in the back-and-forth direction in a plan view as shownin FIG. 8A, and the front end 1 b of the linear side 1 a of the cab box1 is rounded with a radius of curvature r also in a plan view. In theabove mentioned prior-art operator cab, the side of the cab box wherethe door is provided is rounded including the door, so the width of thecab room is narrower at the front and the rear of the operator cab. As aresult, the operator in the prior-art operator cab has not had as muchspace at his feet as in the case of the present invention. In otherwords, with the same width for the operator cab, the embodimentaccording to the present invention, which has partly a linearlyextending side, secures a wider space at the feet of the operator in theoperator cab 53. The door 2, which constitutes the linear side 1 a ofthe cab box 1, also has its rear part extending linearly. As shown inFIG. 8A, even though a little part of the rear end of the door 2 exceedsthe turning radius R when the door 2 is opened, the width L1 of theoperator cab 53 with its door 2 open almost equals that of the prior-artoperator cab, in which the front and the rear of the door slide, so theprotrusion of the door of the operator cab according to the presentinvention does not present any practical problem.

In a case where the door 2 is made larger and heavier, the upper andlower link members 3 and 4, which constitute the link mechanism 20, arestrengthened with rollers 16, which are provided to carry the weight ofthe door 2 as shown in FIG. 9. In this case, plate-like support members(not shown) are provided immediately below the upper and lower linkmembers 3 and 4, and the rollers 16 roll over these support members whenthe door 2 is opened and closed. Each roller 16 comprises a bearingportion 16 b, which extends laterally from the link member 3 or 4, and aroller member 16 a, which is mounted rotatable on the bearing portion 16b. In this case, the rotational axis of the roller member 16 a ispositioned in line with the fixed end 3 a (4 a) and the moving end 3 b(4 b) of the link member 3 or 4. Depending on the weight of the door 2,the roller member 16 a is provided in singularity either on the upperlink member 3 or on the lower link member 4.

In the above described embodiment, the bumper 6 a of the slide member 6is provided with fitting recesses 6 e and 6 f, with which the protrudingparts 11 a and 12 a of the stoppers 11 and 12 are engaged. However,instead, the stoppers 11 and 12 may be provided with fitting recesses,and the bumper 6 a may be provided with protruding parts, which can fitwith these fitting recesses.

Second Embodiment

In the first embodiment, the front part of the door 2 is supported bythe link mechanism 20 while the rear part is supported by the slidemechanism 30. However, it is possible that both the front and rear ofthe door be supported either by a link mechanism or by a slide mechanismalone, so each of such cases is described in the following, wherecomponents identical to those of the first embodiment are indicated bythe same numerals to leave out redundant explanation.

At first, as a second embodiment, a case where both the front and rearparts of the door 2 are supported by a link mechanism 120 is describedin reference to FIG. 11˜FIG. 13. The link mechanism 120 in the secondembodiment comprises a front link member 103 and a rear link member 104,which are positioned, respectively, one in front of the other. One end(fixed end 103 a or 104 a) of each link member is connected pivotally tothe cab box 1 at the upper part thereof, and the other end (moving end103 b or 104 b) is connected pivotally to the door 2 at the upper partthereof, so that both the link members can swing freely.

At the rear pat of the door 2, provided is a bumper 106 designed toengage with the stopper 11, which is provided at the rear pat of the cabbox 1, when the door 2 is opened, and by this engagement, the door 2 iskept in its opened condition. Also, the bumper 106 is designed to engagewith the stopper 12, which is provided approximately at the central partof the cab box 1, when the door 2 is closed, and by this engagement, thedoor 2 is kept in its closed condition. The bumper 106 has the sameshape as the bumper 6 a of the slide member 6 in the first embodiment.

Also, in the second embodiment, when the door 2 is closed as shown inFIG. 12, the closed door lock 7, which is provided at the front part ofthe door 2, engages with the striker 8, which is provided on the cab box1, fixing the front part of the door 2. In this instance, the bumper 106engages with the stopper 12, fixing the rear part of the door 2. On theother hand, when the door 2 is opened as shown in FIG. 13, the openeddoor lock 9, which is provided at the front part of the door 2, engageswith the striker 10, which is provided on the cab box 1, fixing thefront part of the door 2, and in this instance, the bumper 106 engageswith the stopper 11, fixing the rear part of the door 2.

As described above, even though the door 2 is supported only by the linkmechanism 120, because the handle 13, the closed door lock 7 and theopened door lock 9 are provided in concentration at the front part ofthe door 2, the construction of the door 2 is relatively simple.Therefore, it is possible to make the door 2 thin or to make the door 2with a pipe frame. Furthermore, the door 2 can be provided with a window14 at the central part of the door 2.

As shown in FIG. 11, the above embodiment has been described to comprisethe link mechanism 120, which is provided at the upper part of the door2. However, a link mechanism similar to the link mechanism 120 may beprovided additionally at the lower part of the door 2 to support thedoor 2 at the upper and lower parts thereof. The stoppers 11 and 12 andthe bumper 106 as a group can be increased in number in correspondenceto the size or the required strength of the vehicle body of, forexample, the hydraulic mini-shovel 50 (for example, stoppers 11′ and 12′and a bumper 106′ may be added as shown in FIG. 11).

Third Embodiment

As a third embodiment, a case where both the front and rear parts of thedoor 2 are supported only by slide mechanisms 30, 230 and 240 isdescribed in reference to FIG. 14˜FIG. 16. In the third embodiment, theupper front part of the door 2 is supported by the upper slide mechanism230, the lower front part of the door 2 is supported by the lower slidemechanism 240, and the approximate, vertical center of the rear part ofthe door 2 is supported by the slide mechanism 30, which is the same asthe first embodiment.

The upper slide mechanism 230 comprises an upper slide rail 203, whichis attached on the cab box 1 along the upper side of the entrance of thecab box 1, and an upper slide member 303, which slides along the upperslide rail 203. The lower slide mechanism 240 comprises a lower sliderail 204, which is attached on the cab box 1 along the lower side of theentrance, and a lower slide member 304, which slides along the lowerslide rail 204.

Also, in the third embodiment, when the door 2 is closed as shown inFIG. 15, the closed door lock 7, which is provided at the front part ofthe door 2, engages with the striker 8, which is provided on the cab box1, fixing the front part of the door 2, and at the same time, the bumper6 a engages with the stopper 12, fixing the rear part of the door 2. Onthe other hand, when the door 2 is opened as shown in FIG. 16, theopened door lock 9, which is provided at the front part of the door 2,engages with the striker 10, which is provided on the cab box 1, fixingthe front part of the door 2, and at the same time, the bumper 6 aengages with the stopper 11, fixing the rear part of the door 2.

As a result, even though the door 2 is supported only by the slidemechanisms 30, 230 and 240, because the handle 13, the closed door lock7 and the opened door lock 9 are provided in concentration at the frontpart of the door 2, the construction of the door 2 is relatively simple.Therefore, it is possible to make the door 2 thin or to make it with apipe frame. Furthermore, the door 2 can be provided with a window 14 atthe central part of the door 2.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

RELATED APPLICATIONS

This application claims the priority of Japanese Patent Application No.2004-135880 filed Apr. 30, 2004, which is incorporated herein byreference.

1. An operator cab for a construction machine, comprising: a cab box,which has an internal cab room and an entrance into said cab room; adoor, which is attached at said entrance such that said entrance isclosed when said door is moved forward, and said entrance is opened whensaid door is moved rearward; a link member, whose one end is connectedpivotally to said cab box and whose other end is connected pivotally toa front end of said door, said link member capable of freely swinginghorizontally; a closed door lock, which is provided at said front end ofsaid door to engage with a closed door striker, which is provided onsaid cab box, said closed door lock keeping said front end of said doorat a closed position, where said entrance is closed, after said door hasshifted forward in correspondence to a forward swing of said link memberaround a pivot at said one end thereof and has reached said closedposition; an opened door lock, which is provided also at said front endof said door to engage with an opened door striker, which is provided onsaid cab box, said opened door lock keeping said door open after saiddoor has shifted rearward in correspondence to a rearward swing of saidlink member around the pivot of said one end thereof and has opened; anda handle, which is provided also at said front end of said door andinterlocked with said closed door lock and with said opened door lock torelease said closed door striker or said opened door striker fromengagement.
 2. The operator cab set forth in claim 1, wherein: saidconstruction machine comprises a vehicle body, on which said operatorcab is provided to be rotatable.
 3. The operator cab set forth in claim1, wherein: said link member comprises an upper link member and a lowerlink member, which are connected pivotally to an upper front end and alower front end of said door, respectively, said upper and lower linkmembers capable of freely swinging horizontally.
 4. The operator cab setforth in claim 3, wherein: said lower link member is provided below afloor of said cab box, so that said lower link member never intrudes thecab room of said cab box.
 5. The operator cab set forth in claim 1,wherein: at a rear end of said door, a rear slide member is provided toslide back and forth along a slide rail, which is provided externally onsaid cab box, said slide rail extending in the back-and-forth direction,so that the rear end of said door can slide back and forth with respectto said cab box by said rear slide member.
 6. The operator cab set forthin claim 5, wherein: said slide rail is provided approximately at avertical center of an external surface of said cab box in rear of saidentrance, extending in the back-and-forth direction.
 7. The operator cabset forth in claim 1, wherein: the rear end of said door is attached toa rear side of said entrance of said cab box by a rear link member,whose one end is connected pivotally to said cab box and whose other endis connected pivotally to the rear end of said door, said rear linkmember capable of freely swinging horizontally.
 8. The operator cab setforth in claim 1, wherein: part of a side of said cab box that includessaid door in closed condition is flat and extends linearly in theback-and-forth direction in a plan view.